Replaced R410 with ethylene -> -111C!

[LardArse]

Replaced the R410A with Ethylene and without even needing to change the cap tube I've finally hit the triple digit cascade mark. -111C :D It stabilizes here during my 45 minutes of testing, no heat loads yet, but so much more stabler and easier than R410A!

http://bravo.ausgamers.com/lardarse/lard/minus111c.JPG

Here are some details:

High stage R22 1HP
Liquid line of low stage measured off insulated drier -47C
Low stage low side: ~12 HG
Low stage high side: ~ 130 PSI.
No heat loads yet.
Static pressure is 30 PSI
Cap tube on low stage ~ 1.6m of 0.026

Seems like the cap tube that I was using with R410 is quite close. I didn't even need to fine-charge it, just opened up gauge valve, static charged it to ~ 30 PSI, waited for high stage to get cold and then turned her on. Perhaps what Dabit said is very true in which the temps are insensitive to the charge?

How do things look???

[Russell_hq]

I ran your numbers through a capillary tube model im currently looking at. It spewed out a capacity of 263 Watts for your cap tube. Seems kinda high. We will see what happens to the temps when you get a load on that sucker :D

I put sub cooling at 3K.

[LardArse]

Ok here goes
~ 100 to 100+w of heat
evap exit pipe temp -96C
low side 3 PSI
High side 175 PSI
Drier/liquid line temp -41C
suction line -55C
I did charge it more to improve temps. It kept on improving till ~
-96C
Analysis?

[Russell_hq]

These numbers give an increase in capacity to 273 Watts from the cap tube model. Its all theoretical, im just using your numbers to play with it. As you have added more R1170 then an increase in capacity would be expected.

If your ethylene is condensing at 175 PSI, this corresponds to a saturation temperature of -43.4ºC. Seems kinda odd your liquid line temp is higher than the saturation temperature. Whats the temperature at the inlet to the capillary?

[LardArse]

Actually its more like 180 PSI or so. Thats way too high a capacity I need, this is for GPU, perhaps more appropriate for prescotts. The liquid line temp is measured off the drier and this directly feeds the cap tube so it should be quite indicative of the temperature at inlet.
From all these, it seems that the cap tube is too unrestrictive? If so, I will start lengthening it. Also, does lengthening/shortening the cap tube on the low stage affect the interstage/high stage temp in anyway?
PS: Do you have a link for the model? I can't recall where I saw the chart for R1150....

[DaBit]

Congratulations! That starts looking good!

[LardArse]

Thx Dabit. Guess it seems to be worth the mark on my door so far :p:
So sir, should I lengthen the cap tube?

[DaBit]

No idea. I'm using about 10ft of .031" plus some additional feets of .028". But I haven't been able to put a serious load on it yet and perform decent measurements.

[Russell_hq]

The model I used was from this article;

http://www.russellpetrie.plus.com/Documents/R290%20Captube%20Calculation.pdf

Read that and come to your own conclusions for the usefullness of the model.

You can get data on ethene here;

http://webbook.nist.gov/chemistry/fluid/

At 3 PSI, your saturation temp is -100ºC. With exit temps of -96ºC your charge and capillary tube are just about right for the load. For a lower load, i.e. GPU, longer cap tube will give lower temps.

[LardArse]

I am quite curious to know, where are you guys measuring evap temps from? I know without heat load you can easily measure from the base of the evap, but when you put on a pelt or whatever you use, do you measure loaded temps from the side of evap or a custom drilled hole in the base? So far, I measure it from the pipe just out from evap and I know it can get very far from the temps at the base. Under no load, the temp at base is the same as the temp at pipe when I tested it.

[Russell_hq]

I dont measure the evaporator temperature. I use the saturation temperature of the refrigerant at suction pressure as an indication of evaporator temperature. I measure the evaporator exit temperature and compare it to the saturation temperature to get an indication of the evap performance.

The evaporator temperature serves no real purpose here unless you are comparing different evaporators.

[LardArse]

I see. Well it should be closer to the chip's temperature.
Anyways, lengthened it to around 2m of 0.026, too damn restrictive with the same heat load. This heatload is definitely much higher than when benching 3D with 9800 XT the last time I tested with R410. But to be safe, I will shorten her up, the previous cap tube actually seemed quite suitable...

[DaBit]

I made a well into the block side where I sticked in the temp sensor. But if I don't have a sensor: SST plus 5C is quite close on an unloaded block which just doesn't flood

[berkut]

Im not really sure if this is ok, but my latest evap, when loaded with a P4 2.4C @ 3.96ghz/ 1.65V (>100W) holds temps within 3-4C of SST (its flodded)